Spacewalkers' dance of derring-do

When astronaut Mike Fossum joined Piers Sellers Saturday for the first spacewalk of the current shuttle mission, it didn't take long for the rookie to fall under the spell of his unique environment.

"I'm in a dream," he said 90 minutes into the outing, as he watched Russia glide past more than 200 miles below. "Nobody wake me up."

Monday, the duo heads out the hatch for the second of three exquisitely choreographed spacewalks, which rank among the most dangerous activities astronauts undertake. They will install a spare pump on the station and repair part of a transporter system used for space-station construction.

It's some dream.

You ease hand over hand along space-station modules, advancing your safety tether as you go. The star-speckled cosmos and a blue planet form your backdrops. All that stands between you and an inhospitable vacuum – plus 600-degree temperature swings between day and night – is half an inch of fabric, metal, and plastic.

"To go out on a spacewalk is incredibly risky," acknowledges Lt. Col. Edward Fincke, a NASA astronaut who spent 187 days aboard the International Space Station in 2004 and took part in four spacewalks. "But it's also amazing."

NASA's push to fulfill President Bush's outline for sending United States astronauts back to the moon and later, perhaps, to Mars has fanned the old debate over whether exploration can be accomplished more cheaply and efficiently with unmanned spacecraft.

It comes as no surprise that here at the Johnson Space Center, the epicenter of the US manned spaceflight program, the role of humans in space exploration is seen as indispensable. And for many astronauts, a key step to taking part in that effort is trading their signature blue jumpsuits for a glistening spacesuit.

Each suit tips the scale at 300 pounds and carries a price tag that would make Armani blush. The cash register has cha-chinged for a dozen or so suits in NASA's wardrobe, at roughly $10 million each. Sizes? Medium, large, and extra large.

The road to an eventual spacewalk begins as new astronauts are evaluated to determine their potential roles as crew members, notes Glenn Lutz, deputy manager of the EVA (Extravehicular Activity, or spacewalks) office here.

"We're looking for brain power – people who can think on their feet, are good with their hands," and have good recall, he says.

The job also is physically demanding: While the spacesuit and hardware are weightless in space, they still have mass and require effort to move. The tools astronauts use look much like those you'd find down the aisle at Home Depot, but they have heftier handles and tethers – and the materials they are made from must be consistent throughout the tool to avoid uneven expansion and contraction as they warm and chill.

"Think of trying to repair a refrigerator while you're wearing ski gloves," Mr. Lutz says.

Astronauts preparing for an EVA train in a huge pool that boasts submerged mock-ups of space-station modules and the shuttle. Each hour an astronaut spends on a spacewalk has an average of seven hours of pool training behind it, Lutz says. That training covers every step of a planned spacewalk.

Because of the hiatus in shuttle flights after the Columbia disaster in 2003 and the loss of foam debris during last year's first "return to flight" mission, Mr. Fossum and Dr. Sellers have put in additional training time – up to 15 hours in the tank for each hour of their three spacewalks, adds Lieutenant Colonel Fincke, a member of Sellers's astronaut class.

For all the training, the little things can still throw astronauts a curve.

On Saturday's 7-1/2-hour spacewalk, Fossum and Sellers spent 20 minutes with mission controllers trying to figure out why Fossum's retractable tether wouldn't take up slack as he moved back toward its reel. The solution: Release the reel's rewind brake.

In the end, it was a minor glitch in a spacewalk that gave NASA "fantastic results" from experiments to see how well an extension to the shuttle's robotic arm could perform as a crew platform for repairing shuttle tiles in space, notes Tomas Gonzales-Torres, lead EVA officer for the mission.

On EVAs, the timeline is king – even when things go a bit haywire.

Fincke recalls that during his stay on the space station, he and cosmonaut Gennady Padalka were in the midst of their third spacewalk when they noticed the Earth had dramatically changed position in the night sky from their vantage point. The system that controls the station's orientation with respect to the sun and Earth (the attitude-control system) had failed, and the station was slowly tumbling. And the duo had lost contact with mission control in Houston as well.

"There wasn't much we could do about it, and we were coming within range of Russian ground stations, so we kept working," he says. Sure enough, about 8 minutes later, Russian ground controllers called up to warn the two to keep clear of the station's thrusters so they could nudge the station into the right attitude.

Once the shuttle program ends, NASA is likely to put much less focus on mission-specific EVA training. Instead, it will probably put more emphasis during training on generic skills that spacewalking astronauts can apply to a wider range of situations than, say, repairing the Hubble Space Telescope, Fincke suggests.

"These EVAs are an important investment," he continues. "We're starting to help ourselves with some of our maintenance tasks by having more-enhanced robotics. The new Canadian robotic arm is going to have something called 'Dexter,' which will be able to handle some fine-scale tasks and change out some boxes" on the station's exterior.

"But we still need humans in the loop," he maintains. "The things we learn about our spacewalking, how to train for it, and how to maintain our spacesuits on orbit will be applicable" for a range of future missions.